Recognizing that the earlier SRT scheme on a rhombic lattice does not have the additional degrees of freedom [1]}, Ref. [2]} proposed another rectangular SRT-LBM using additional particle velocities whose equilibria, involving their weights and scaling factors, obtained via solving a quadrature problem, and validated for the Taylor-Green vortex flow using moderate grid aspect ratios (defined in the next section). Note that using additional particle velocities adds to the computational overhead and may complicate the implementation of the boundary conditions. A different rectangular SRT-LB scheme with extended equilibrium distribution functions was proposed in Ref. [3]}, which was, however, found to be stable only if the grid aspect ratio is above \(0.3\) . Recently, Ref. [4]} adopted a different approach by introducing artificial source terms obtained via a coordinate/velocity transformation, which was found to be severely limited to using grid aspect ratio is larger than \(0.5\) . Moreover, none of the above rectangular LB formulations are flexible enough to adjust the shear and bulk viscosities independently.
